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[SOUND].

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We've learned how to write
the simplest possible module.

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However, it really didn't
do much of anything,

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because we were only talking about
the namespacing aspect of modules.

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Next we're going to take
a look at creating a mix-in.

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If we want to mix in behavior to a class,
we have to use the include method.

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Unsurprisingly, based on the name,
that will include all of the methods

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in the module in the class
that we're working with.

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In order to make our modules
actually do something,

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it needs to be included in a class.

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Let's see how that works
now using workspaces.

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Okay, so let's go ahead and

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create our very first module that
does something when we include it.

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So we're gonna call this fetcher.rb.

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And let's go ahead and
create a class for a dog.

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And the dog is going to have a name.

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So we'll go ahead and
create a new dog instance here.

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Here is Fido.

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Okay now we're gonna make a module,
that we can include in the dog class,

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in case we wanted a dog
to be able to fetch.

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So we'll call this module fetcher.

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And now we'll create
a module called fetch,

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which is going to take one argument,
which is the item that is being fetched.

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And then whatever is happening here we'll
say, I'll bring that item right back.

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What we have to do is include
the fetcher module in the Dog class.

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So, once we have this module
here included in the Dog class,

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we can go back up here and any of the
methods that are in this fetcher module

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will be included or mixed in to the Dog
class and we have access to them.

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So we could now say something
like dog.fetch, and

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then passing an item which
is going to be ball.

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So if we run this,
let's go ahead and see what happens.

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Dog says I'll bring that ball right back.

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Now the benefit for

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something like this is if we had
another class, let's say, called Cat.

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We could say cat is Cat.new.

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What's a good name for a cat?

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So we'll create a new cat called Garfield,
and

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now we can say cat.fetch laser pointer.

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So if we run that, because the Cat
class includes the fetcher module,

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we get all of the methods inside of there.

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And if we run it again we can see
that the cat says it's going to

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bring the laser pointer right back.